Borate glass for laser use



U111 LCU.

3,254,031 BORATE GLASS FOR LASER USE Paul F. De Paolis and Paul B.Mauer, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester,N.Y., a corporation of New Jersey N Drawing. Filed June 27, 1962, Ser.No. 205,540 3 Claims. (Cl. 252-301.4)

This invention relates to laser materials of improved efiiciency, laserreferring to light amplification by stimu lated emission of radiation.

The laser action of certain materials has been noted, and the reports ofthe use of the intense energy contained in the beam of light from alaser have been given. For example, see A. L. Schwalow and C. H. Townes,Phys. Rev., 112, 1940 (1958); E. Snitzer, Optical Maser Ac tion inBarium Crown Glass, Phys. Rev., Letters, vol. 7, #12, Dec. 13, 1961, p.444; The Wall Street Journal, Friday, April 13, 1962, p. 14; and Time,April 20, 1962, p. 103.

Cross reference is made to our cofiled application S.N. 205,539 onphosphate lasers.

We have found that by means of certain novel compositions, lasermaterials of improved efficiency are obtained. For example, thethreshold value at which materials according to the present inventionbegin to exhibit negative absorption and thus initiate laser action islower than with materials previously known, even though our materialsfiuoresce with an efficiency no greater than other known materials. Inother words, although fluorescence is an integral part of lasing,increased lasing does not depend solely on increased fluorescence.

It is a primary object of our invention to provide improved lasermaterials and particularly laser materials having a lower thresholdvalue and/ or greater efiiciency. It is also an object of the presentinvention to produce a glass which is easy to manufacture, mold andpolish to form a laser. In this latter connection, the preferredembodiment of the invention is superior to lasers containing only La, Baand B oxides plus the sensitizing impurity. According to the presentinvention, thorium oxide in substantial amounts to 30% of the total byweight) is included in a batch containing 30 to 40% boric oxide, 30 to50% lanthanum oxide plus barium oxide and .1 to 10% (preferably .3 to3%) of neodymium oxide, which batch is mixed and fused to make a glass.The b-oric oxide for convenience is usually introduced in the form ofboric acid.

Example 1 Various embodiments of the invention start with a batchasfollows:

Percent by wt.

to which is added Nd O in various amounts between 0.1 and 10% of theweight of the above base, which batch is then fused as a glass. Theseare excellent lasers.

larly desirable for laser use.

proximately M1." in diameter and 2" long, with polished- 3,254,031atented May 31, 1966 7 Example 2 Similarly other examples of theinvention start with a batch as follows:

to which is added Nd o in amounts between 0.1 and 10% of base whichbatch is then fused to form a glass.

The fine optical homogeneity of these materials and their ease offabrication into rods renders them particusemi-reflecting ends which areusually flat and parallel, but which in some lasers are curved.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

We claim:

1. An article for use in a laser comprising a laser rod whose length isgreater than its diameter, which has polished ends and which is a glassformed by fusion of a batch consisting essentially of at leastsubstantial amounts of each of 1.8.20 BaO, ThO B 0 and Nd O the LaO andBaO totaling 30% to by weight, the ThO being between l0% and 30% byweight, the B 0 being between 30% and 40% by weight and the Nd o between0.1% and 10% by weight.

2. An article for use in a laser comprising a laser rod whose length isgreater than its diameter, which has polished ends and which is of amaterial consisting essentially of glass formed by fusion of a batchcontaining sensitizer and a base having substantially the followingcomposition:

Percent by wt. 1.3.205 BaO 21 Th0; 20 B 0 37 to which, as thesensitizer, has been added Nd O in an amount between 0.1 and 10% of theweight of the base.

3. An article for use in a laser comprising a laser rod whose length isgreater than its diameter, which has polished ends and which is of amaterial consisting essentially of glass formed by fusion of a batchcontaining sensitizer and a base having substantially the followingcomposition:

A typical laser rod is an; b

3,354,031 3 4 to which, the sensitizer, has been added Nd O in an OTHERREFERENCES amount between 0.1 and 10% of the weight of the base.pringsheim, Fluorescene and phosphorescence,

References Cited by the Examiner lished 1949 by Interscience Publishers,New York city (pages 474-478). UNITED STATES PATENTS 5 Snitzer, OpticalMaser Action in Barium Crown 2,115,633 5/1938 Long 105-47 Glass, Phys.Rev. Letters, volume 7, December 13, 1961 2,434,146 1/1948 De Paohs106-47 (page 444), 3,082,101 3/1962 Geflfcken et a1. 106-47 10 E.Primary Examiner. 338,334 11/1930 Great Britain. H. .MCCARTHY, AssistantExaminer.

412,110 6/1934 Great Britain.

1. AN ARTICLE FOR USE IN A LASER COMPRISING A LASER ROD WHOSE LENGTH ISGREATER THAN ITS DIAMETER, WHICH HAS POLISHED ENDS AND WHICH IS A GLASSFORMED BY FUSION OF A BATCH CONSISTING ESSENTIALLY OF AT LEASTSUBSTANTIAL AMOUNTS OF EACH LA2O3, BAO, THO2, B2O3 AND ND2O3, THE LAO2AND BAO TOTALING 30% TO 50% BY WEIGHT, THE THO2 BEING BETWEN 10% AND 30%BY WEIGHT, THE B2O3 BEING BETWEEN 30% AND 40% BY WEIGHT AND THE ND2O3BETWEEN 0.1% AND 10% BY WEIGHT.